1. Field of the Invention
The present invention relates to a variable valve mechanism that varies the lift and operating angle of the valve continuously or in steps depending on the operating condition of an internal combustion engine.
2. Description of Related Art
An exemplary variable valve mechanism of the prior art as discussed in Laid-open Japanese Patent Application No. 2001-263015 and shown in FIG. 15 comprises a first intervening member 84 pressed by a rotating cam (not shown) and a pair of second intervening members 86 provided on the left and right sides of the first intervening member 84 to press valves 91 via rocker arms 81 respectively mounted rotatably on a support shaft 82, wherein the relative rotating angle between the first intervening member 84 and the second intervening member 86 is changed by sliding a slider gear 89 via a control shaft 90 inserted slidably in the center of the support shaft 82, which the slider gear 89 being provided so that splines 87 and 88 formed inside of the first intervening member 84 and the second intervening member 86 can engaged.
Such a variable valve mechanism has the following problems:
(1) Machining of splines 87, 88 on the internal surfaces of the first intervening member 84 and the second intervening member 86 is difficult;
(2) In order to maintain a necessary sliding distance of the slider gear 89, there is a limit in shortening the span between the first intervening member 84 and the second intervening member 86 so that it is difficult to make the variable valve mechanism more compact;
(3) There are cases where fluctuations occur in the lift among valves 91 as only a portion of each second intervening member 86 is supported by the support shaft 82 among the first intervening member 84 and a pair of second intervening members 86 with both the first intervening member 84 and second intervening members 86 being unstable. In particular, when the lift among valves is small, the fluctuation of the lift becomes too large making the combustion of the internal combustion engine unstable; and,
(4) Since the slider gear 89 typically has several dozen teeth, there is no guarantee that all of the teeth are in contact with the teeth of splines 87 and 88 so that it becomes impossible to change the lift smoothly from a low lift to a high lift when some teeth of the slider gear 89 cause irregular shifting.
At least one object of the current invention is to provide an inexpensive variable valve mechanism that solves the abovementioned problems, which is compact and has no variation in the left and right valve lift.
In order to solve the aforementioned problems, the variable valve mechanism of this invention includes the following features. A first intervening member rotates a small angle rotation about an axis of a support shaft by being pressed by a rotating cam. A second intervening member lifts a valve by making a small angle rotation about an axis of said support shaft together with said first intervening member thus pressing a cam corresponding part of a rocker arm. A control shaft is provided concentrically with said support shaft A slider moves with said control shaft. A slanted part, which contacts with said slider, is formed diagonally relative to said slider""s movement direction. Finally, a relative rotation angle control device varies the relative rotation angle of said first intervening member and said second intervening member by pressing said slanted part in a direction substantially perpendicular to said slider""s movement direction by moving said slider together with said control shaft. Thereby, the valve""s lift and operating angle is varied continuously or in steps in response to the operating condition of an internal combustion engine. The cam corresponding part is a part pressed against the rotating cam in correspondence with the first intervening member and the second intervening member in that order.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purpose of illustration and not as a definition of the invention, for which reference should be made to the appended claims.